FOXP3 (forkhead box P3) is a protein involved in immune system responses. The human FOXP3 genes contain 11 coding exons. Exon-intron boundaries are identical across the coding regions of the mouse and human genes. By genomic sequence analysis, the FOXP3 gene maps to the p arm of the X chromosome (specifically, Xp11.23). A member of the FOX protein family, FOXP3 appears to function as a master regulator in the development and function of regulatory T cells. While the precise control mechanism has not yet been established, FOX proteins belong to the forkhead/winged-helix family of transcriptional regulators and are presumed to exert control via similar DNA binding interactions during transcription.